Born in Eugene, Oregon, Ainge starred in high school on his football team and led North Eugene High School to back-to-back state basketball championships in 1976 and 1977, earning all-state honors both years; he was considered one of the top prep football recruits in the state of Oregon. As a junior, he was named to the 1977 Parade magazine High School All-America team. Ainge is the only person to be a high school first team All-American in football, basketball, and baseball.

Ainge played basketball at Brigham Young University (BYU) and became a household name[peacock term] after hitting one of the best-known shots in NCAAMarch Madness history against Notre Dame in 1981.[citation needed] His coast-to-coast drive with seven seconds remaining gave the Cougars a one-point win. Ainge concluded his senior year by winning the Eastman Award, as well as the John R. Wooden Award—given to the best collegiate player in the nation. During his four-year career at BYU, Ainge was an All-American, a two-time First Team Academic All-American, the WAC Player of the Year and a four-time All-WAC selection. He concluded his college career having scored in double figures in 112 consecutive games, an NCAA record at that time.

Ainge was selected in baseball's 1977 amateur draft by the Toronto Blue Jays. He made it to the major leagues with the Blue Jays in 1979 while still in college. Mostly a second baseman, he played third base and outfield positions as well, hitting .220 in his baseball career with 2 home runs and 146 hits in 211 games. He is the youngest player in Blue Jays history to hit a home run, at 20 years and 77 days.

After three years with the Blue Jays, Ainge decided to pursue a career in basketball and was chosen in the 1981 NBA draft by the Boston Celtics, who had to buy out Ainge's contract from the Blue Jays after a legal battle.

Not everything went well for Ainge in basketball at first. He had a terrible first day of practice, "shooting 0–2547", Larry Bird wrote in his autobiography Drive: The Story of My Life. Celtics head coach Bill Fitch gave Ainge a rough time, saying his batting average was better than his shooting percentage on the basketball court. But Ainge became an important piece of the Celtics teams that won the NBA title in 1984 and 1986.

Ainge was known as a brash, hard-nosed player who often infuriated opponents. In a 1983 playoff game against Atlanta, he called 7-foot, 1-inch Tree Rollins a sissy, whereupon Rollins elbowed Ainge in the face. Ainge tackled Rollins and the two began wrestling. Tree bit Ainge's middle finger so hard that it required two stitches to keep the tendon together. Ainge was ejected from the contest for starting the fight. The incident prompted the headline "Tree Bites Man" on the April 25, 1983, Boston Herald.[1] While playing for the Phoenix Suns, Ainge got into a tussle with Michael Jordan at midcourt; both were given a technical foul. In a 1994 postseason game, Ainge rifled an inbounding pass at the head of Houston Rockets guard Mario Elie, striking him in the face, snapping his neck back.[2][3][4]

In 1990, Ainge was traded to the Portland Trail Blazers for Byron Irvin and draft picks. Being a native of Oregon, he was considered a hometown favorite by Blazers fans. He helped the Blazers reach the 1992 NBA Finals, only to succumb to the Chicago Bulls in six games. On June 5, he scored nine points in the extra period to tie an all-time NBA record for most points in an overtime during a finals game.

After the 1991–92 season, Ainge became a free agent. He had stated in media interviews that he ideally wanted to stay in Portland and would contact Blazers management before seriously entertaining offers from other teams. On July 1, 1992, however, Ainge signed a contract with the Phoenix Suns on his first day of free agency.

The Phoenix Suns were a team looking for a new identity. They inaugurated a new home (America West Arena), hired a new head coach (Paul Westphal), and acquired a new superstar (Charles Barkley). The team also redesigned their logo and uniform when they signed free agent Ainge prior to the 1992–93 season, figuring that his experience would help the team during the playoffs. Ainge responded by scoring 11.8 points per game as the Suns went 62–20 that year and reached the NBA finals, where they lost to Michael Jordan's Bulls in six games.

On January 18, 1994, he became the second man ever to hit 900 three-point shots in NBA history (he made 1,002 three pointers for his career), and he scored 11,964 points for an average of 11.5 points per game, 2,768 rebounds for an average of 2.7, and 4,199 assists, an average of four per game, over 1,042 NBA games.

While a player with the Blue Jays, Ainge opened a national chain of hat stores which he has since sold. He has volunteered his time at a number of charitable organizations and has held a number of jobs since retiring. He became head coach of the Phoenix Suns in 1996. His resignation from the Suns coaching job was a sudden one; he cited a need to spend more time with his family. He was replaced by assistant coach Scott Skiles. In 2003, he was hired as the Executive Director of Basketball Operations for the Celtics. Ainge also served as a commentator for the NBA on TNT.

Ainge has often been controversial in his role as a Celtics executive, trading popular players such as three-time All-Star Antoine Walker (earning himself the nickname "Trader Dan") and having personality conflicts with then-head coach Jim O'Brien (which eventually led to O'Brien's departure to the Philadelphia 76ers). However, Ainge kept the support of both the Celtics' ownership group and—perhaps most importantly—legendary former head coach Red Auerbach, who was employed by the team as a "senior assistant" until his death in October 2006.

The 2006–07 Celtics finished with a 24–58 record, second-worst in the team's history. Following the season, Paul Pierce, team captain and face of the franchise, expressed frustration with the team's failures. He requested a trade to a contender if management were unable to acquire veteran talent of Pierce's caliber.

Ainge responded with two bold moves that changed the franchise's fortunes almost overnight: the 2007 trades for the Minnesota Timberwolves' Kevin Garnett and the Seattle SuperSonics' Ray Allen immediately returned the Celtics to the ranks of the NBA's elite franchises for the first time since the early 1990s. Together with Pierce, they formed a new "Big Three" and led the Celtics to the NBA's best record (66–16) during the 2007–08 season. It was the most dramatic single-season improvement in league history (42 wins more than the previous year), and it earned Ainge the NBA Executive of the Year Award.

Boston faced the Los Angeles Lakers in the 2008 NBA Finals, renewing the long rivalry between the two teams. The Celtics won the series in six games, giving the franchise its 17th NBA championship. Danny Ainge held the trophy for the first time since winning in 1986. In October 2008, after the Celtics' championship season, he was promoted to President of Basketball Operations.[5]

On May 3, 2010 Ainge was fined $25K for tossing a towel to distract a Cleveland Cavaliers player shooting a free throw during game 2 of the Eastern Conference Semifinals.[1]

In 2013, Ainge traded Garnett and Pierce, along with Jason Terry and D.J. White, to the Brooklyn Nets in exchange for five players plus the Nets' first-round picks in 2014, 2016 and 2018.[6] Boston also received the rights to swap picks with Brooklyn in 2017.[7] It is widely considered one of the most lopsided trades in league history.[8]

On August 22, 2017, Ainge made another blockbuster deal, trading All-Star point guard Isaiah Thomas, as well as Jae Crowder, Ante Žižić and the rights to the Nets' 2018 first-round draft pick, to the Cleveland Cavaliers for All-Star Kyrie Irving.[9]

Ainge and his wife, Michelle, currently reside in Wellesley, Massachusetts; they have six children (Ashlee, Austin, Tanner, Taylor, Cooper and Crew). Austin Ainge is director of player personnel for the Boston Celtics[10] and like his father, played basketball at BYU. Tanner Ainge is a lawyer and a former political candidate.